1. Field of the Invention
This invention relates to the field of industrial waste disposal ovens.
2. Description of the Prior Art
As the population increases, the necessity for developing waste management techniques increases in parallel. One dilemma facing modern day waste management facilities is the need to efficiently dispose of solid materials while simultaneously protecting the environment from the harmful by-products of the disposal process. This dilemma is exacerbated by the fact that many materials disposed of by the consuming public are not biodegradable and when submitted to waste managers, may not be simply buried and left for future generations to deal with. As history has shown, burying of non-biodegradable stockpiles does not prevent them or their byproducts from resurfacing and forming toxic waste pools and fumes at some point in the future.
A common disposal alternative to burying materials is incineration. One form of incineration involves heating material in the presence of oxygen until combustion occurs. Combusting most materials is effective in reducing the actual solid composition but is recognized as creating a different set of problems. Combustion contributes to air pollution in several gaseous forms. The by-products of combusted materials typically produce carbon dioxide which has been asserted to be a contributor to poor breathable air quality and the green house effect. The thickness of smoke produced has a visible effect on the quality of air in the vicinity of a waste incinerator. Non-biodegradable materials often expel noxious gases as well as large quantities of volatile organic compounds because of the prominent presence of oxygen. Volatile organic compounds, when uncontrolled in their management, quickly escape into the atmosphere as air pollutants and/or fall to earth becoming ground and water contaminants.
One common waste material whose decomposition has deleterious effects on the environment is vulcanized tire rubber. Typical American drivers can go through a set of four tires every two years equating to over 250 million tires disposed of each and a year. This is equivalent to nearly 4 million tons of rubberized material a year. Entire landfills and sections of garbage dumps are dedicated to the management of these items. Unfortunately, mounds of old rubber tires stacked several feet high become eyesores and occupy valuable space. The various adverse aspects of scrap tire disposal has led 33 states to ban whole tires from landfills while a dozen ban any form of scrap tires altogether. Where recycling of old rubber tires is economically unfeasible, incineration is the next best alternative. When burned, thick black plumes of obnoxious smoke and malodorous gases surround the area. The oxidized results are harmful to the air and ground they seep into. The lands used for tire burning are generally unusable for other purposes and may remain barren of vegetation for several years.
One technique that has proven effective in overcoming the deficiencies of oxygen feed combustion for waste material incineration is pyrolysis. Pyrolysis involves heating material sans the presence of oxygen or in an oxygen depleted environment. Chemical bonds are broken under pressure and operating temperatures typically above 800° F. Since the presence of oxygen is kept to a minimum, less gassing off occurs and less volatile organic compounds and smoke are produced. A majority of the material is converted to char while other by-products may include oils and syn-gas (the name given to gases of varying composition that are generated in the steam reforming of liquid hydrocarbons in some types of waste-to-energy gasification facilities) all of which can be energy rich and reused in other applications.
Most pyrolytic ovens use systems with numerous mechanical parts to move material through a heated passageway. A common example is a horizontal conveyor belt carrying shredded rubber tires through a long chamber. These ovens suffer from the deficiencies of any machine that includes several moving parts. Every additional part used is a potential point of breakdown for the oven. In a high temperature, pressurized environment, the small components of the system tend to fail or deteriorate frequently causing wasted time, extra labor for maintenance, replacement of parts and an extra overall expense. Coupling the need for many moving parts with the requirement that each component must function at very high temperatures means more expense is incurred in purchasing materials for constructing the oven.
One proposed solution uses an inclined chute oven where material is dropped onto a singular heated ramp and makes its way to an exit. A construction of this kind is seen in U.S. Pat. No. 7,032,525 to Edmondson. Ovens of this configuration lack flexibility in altering the movement rate and retention time of material and are susceptible to char buildup at the ramp's end when material is insufficiently incinerated. Ovens of this configuration also appear to lack flexibility in the control of heat exposure at various points of material freefall.
It can be seen then that a need exists for a more reliable pyrolytic oven capable of adjusting the retention time and heat exchange efficiency of material for sufficient thermal conversion while safely dispatching hydrocarbon gases.